tiny_obj_loader.cc

//
// Copyright 2012-2015, Syoyo Fujita.
//
// Licensed under 2-clause BSD liecense.
//

//
// version 0.9.14: Support specular highlight, bump, displacement and alpha map(#53)
// version 0.9.13: Report "Material file not found message" in `err`(#46)
// version 0.9.12: Fix groups being ignored if they have 'usemtl' just before 'g' (#44)
// version 0.9.11: Invert `Tr` parameter(#43)
// version 0.9.10: Fix seg fault on windows.
// version 0.9.9 : Replace atof() with custom parser.
// version 0.9.8 : Fix multi-materials(per-face material ID).
// version 0.9.7 : Support multi-materials(per-face material ID) per
// object/group.
// version 0.9.6 : Support Ni(index of refraction) mtl parameter.
//                 Parse transmittance material parameter correctly.
// version 0.9.5 : Parse multiple group name.
//                 Add support of specifying the base path to load material file.
// version 0.9.4 : Initial suupport of group tag(g)
// version 0.9.3 : Fix parsing triple 'x/y/z'
// version 0.9.2 : Add more .mtl load support
// version 0.9.1 : Add initial .mtl load support
// version 0.9.0 : Initial
//

#include <cstdlib>
#include <cstring>
#include <cassert>
#include <cmath>
#include <cstddef>
#include <cctype>

#include <string>
#include <vector>
#include <map>
#include <fstream>
#include <sstream>

#include "tiny_obj_loader.h"


namespace tinyobj {

#ifdef __clang__
#pragma clang diagnostic ignored "-Wold-style-cast"
#pragma clang diagnostic ignored "-Wsign-conversion"
#pragma clang diagnostic ignored "-Wmissing-prototypes"
#if __has_warning("-Wzero-as-null-pointer-constant")
#pragma clang diagnostic ignored "-Wzero-as-null-pointer-constant"
#endif
#endif

#define TINYOBJ_SSCANF_BUFFER_SIZE  (4096)

struct vertex_index {
  int v_idx, vt_idx, vn_idx;
  vertex_index(){}
  vertex_index(int idx) : v_idx(idx), vt_idx(idx), vn_idx(idx){}
  vertex_index(int vidx, int vtidx, int vnidx)
      : v_idx(vidx), vt_idx(vtidx), vn_idx(vnidx){}
};
// for std::map
static inline bool operator<(const vertex_index &a, const vertex_index &b) {
  if (a.v_idx != b.v_idx)
    return (a.v_idx < b.v_idx);
  if (a.vn_idx != b.vn_idx)
    return (a.vn_idx < b.vn_idx);
  if (a.vt_idx != b.vt_idx)
    return (a.vt_idx < b.vt_idx);

  return false;
}

struct obj_shape {
  std::vector<float> v;
  std::vector<float> vn;
  std::vector<float> vt;
};

static inline bool isSpace(const char c) { return (c == ' ') || (c == '\t'); }

static inline bool isNewLine(const char c) {
  return (c == '\r') || (c == '\n') || (c == '\0');
}

// Make index zero-base, and also support relative index.
static inline int fixIndex(int idx, int n) {
  if (idx > 0) return idx - 1;
  if (idx == 0) return 0;
  return n + idx; // negative value = relative
}

static inline std::string parseString(const char *&token) {
  std::string s;
  token += strspn(token, " \t");
  size_t e = strcspn(token, " \t\r");
  s = std::string(token, &token[e]);
  token += e;
  return s;
}

static inline int parseInt(const char *&token) {
  token += strspn(token, " \t");
  int i = atoi(token);
  token += strcspn(token, " \t\r");
  return i;
}


// Tries to parse a floating point number located at s.
//
// s_end should be a location in the string where reading should absolutely
// stop. For example at the end of the string, to prevent buffer overflows.
//
// Parses the following EBNF grammar:
//   sign    = "+" | "-" ;
//   END     = ? anything not in digit ?
//   digit   = "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9" ;
//   integer = [sign] , digit , {digit} ;
//   decimal = integer , ["." , integer] ;
//   float   = ( decimal , END ) | ( decimal , ("E" | "e") , integer , END ) ;
//
//  Valid strings are for example:
//   -0	 +3.1417e+2  -0.0E-3  1.0324  -1.41   11e2
//
// If the parsing is a success, result is set to the parsed value and true 
// is returned.
//
// The function is greedy and will parse until any of the following happens:
//  - a non-conforming character is encountered.
//  - s_end is reached.
//
// The following situations triggers a failure:
//  - s >= s_end.
//  - parse failure.
// 
static bool tryParseDouble(const char *s, const char *s_end, double *result)
{
	if (s >= s_end)
	{
		return false;
	}

	double mantissa = 0.0;
	// This exponent is base 2 rather than 10.
	// However the exponent we parse is supposed to be one of ten,
	// thus we must take care to convert the exponent/and or the 
	// mantissa to a * 2^E, where a is the mantissa and E is the
	// exponent.
	// To get the final double we will use ldexp, it requires the
	// exponent to be in base 2.
	int exponent = 0;

	// NOTE: THESE MUST BE DECLARED HERE SINCE WE ARE NOT ALLOWED
	// TO JUMP OVER DEFINITIONS.
	char sign = '+';
	char exp_sign = '+';
	char const *curr = s;

	// How many characters were read in a loop. 
	int read = 0;
	// Tells whether a loop terminated due to reaching s_end.
	bool end_not_reached = false;

	/*
		BEGIN PARSING.
	*/

	// Find out what sign we've got.
	if (*curr == '+' || *curr == '-')
	{
		sign = *curr;
		curr++;
	}
	else if (isdigit(*curr)) { /* Pass through. */ }
	else
	{
		goto fail;
	}

	// Read the integer part.
	while ((end_not_reached = (curr != s_end)) && isdigit(*curr))
	{
		mantissa *= 10;
		mantissa += static_cast<int>(*curr - 0x30);
		curr++;	read++;
	}

	// We must make sure we actually got something.
	if (read == 0)
		goto fail;
	// We allow numbers of form "#", "###" etc.
	if (!end_not_reached)
		goto assemble;

	// Read the decimal part.
	if (*curr == '.')
	{
		curr++;
		read = 1;
		while ((end_not_reached = (curr != s_end)) && isdigit(*curr))
		{
			// NOTE: Don't use powf here, it will absolutely murder precision.
			mantissa += static_cast<int>(*curr - 0x30) * pow(10.0, -read);
			read++; curr++;
		}
	}
	else if (*curr == 'e' || *curr == 'E') {}
	else
	{
		goto assemble;
	}

	if (!end_not_reached)
		goto assemble;

	// Read the exponent part.
	if (*curr == 'e' || *curr == 'E')
	{
		curr++;
		// Figure out if a sign is present and if it is.
		if ((end_not_reached = (curr != s_end)) && (*curr == '+' || *curr == '-'))
		{
			exp_sign = *curr;
			curr++;
		}
		else if (isdigit(*curr)) { /* Pass through. */ }
		else
		{
			// Empty E is not allowed.
			goto fail;
		}

		read = 0;
		while ((end_not_reached = (curr != s_end)) && isdigit(*curr))
		{
			exponent *= 10;
			exponent += static_cast<int>(*curr - 0x30);
			curr++;	read++;
		}
		exponent *= (exp_sign == '+'? 1 : -1);
		if (read == 0)
			goto fail;
	}

assemble:
	*result = (sign == '+'? 1 : -1) * ldexp(mantissa * pow(5.0, exponent), exponent);
	return true;
fail:
	return false;
}
static inline float parseFloat(const char *&token) {
  token += strspn(token, " \t");
#ifdef TINY_OBJ_LOADER_OLD_FLOAT_PARSER
  float f = (float)atof(token);
  token += strcspn(token, " \t\r");
#else
  const char *end = token + strcspn(token, " \t\r");
  double val = 0.0;
  tryParseDouble(token, end, &val);
  float f = static_cast<float>(val);
  token = end;
#endif
  return f;
}


static inline void parseFloat2(float &x, float &y, const char *&token) {
  x = parseFloat(token);
  y = parseFloat(token);
}

static inline void parseFloat3(float &x, float &y, float &z,
                               const char *&token) {
  x = parseFloat(token);
  y = parseFloat(token);
  z = parseFloat(token);
}

// Parse triples: i, i/j/k, i//k, i/j
static vertex_index parseTriple(const char *&token, int vsize, int vnsize,
                                int vtsize) {
  vertex_index vi(-1);

  vi.v_idx = fixIndex(atoi(token), vsize);
  token += strcspn(token, "/ \t\r");
  if (token[0] != '/') {
    return vi;
  }
  token++;

  // i//k
  if (token[0] == '/') {
    token++;
    vi.vn_idx = fixIndex(atoi(token), vnsize);
    token += strcspn(token, "/ \t\r");
    return vi;
  }

  // i/j/k or i/j
  vi.vt_idx = fixIndex(atoi(token), vtsize);
  token += strcspn(token, "/ \t\r");
  if (token[0] != '/') {
    return vi;
  }

  // i/j/k
  token++; // skip '/'
  vi.vn_idx = fixIndex(atoi(token), vnsize);
  token += strcspn(token, "/ \t\r");
  return vi;
}

static unsigned int
updateVertex(std::map<vertex_index, unsigned int> &vertexCache,
             std::vector<float> &positions, std::vector<float> &normals,
             std::vector<float> &texcoords,
             const std::vector<float> &in_positions,
             const std::vector<float> &in_normals,
             const std::vector<float> &in_texcoords, const vertex_index &i) {
  const std::map<vertex_index, unsigned int>::iterator it = vertexCache.find(i);

  if (it != vertexCache.end()) {
    // found cache
    return it->second;
  }

  assert(in_positions.size() > (unsigned int)(3 * i.v_idx + 2));

  positions.push_back(in_positions[3 * i.v_idx + 0]);
  positions.push_back(in_positions[3 * i.v_idx + 1]);
  positions.push_back(in_positions[3 * i.v_idx + 2]);

  if (i.vn_idx >= 0) {
    normals.push_back(in_normals[3 * i.vn_idx + 0]);
    normals.push_back(in_normals[3 * i.vn_idx + 1]);
    normals.push_back(in_normals[3 * i.vn_idx + 2]);
  }

  if (i.vt_idx >= 0) {
    texcoords.push_back(in_texcoords[2 * i.vt_idx + 0]);
    texcoords.push_back(in_texcoords[2 * i.vt_idx + 1]);
  }

  unsigned int idx = static_cast<unsigned int>(positions.size() / 3 - 1);
  vertexCache[i] = idx;

  return idx;
}

void InitMaterial(material_t &material) {
  material.name = "";
  material.ambient_texname = "";
  material.diffuse_texname = "";
  material.specular_texname = "";
  material.specular_highlight_texname = "";
  material.bump_texname = "";
  material.displacement_texname = "";
  material.alpha_texname = "";
  for (int i = 0; i < 3; i++) {
    material.ambient[i] = 0.f;
    material.diffuse[i] = 0.f;
    material.specular[i] = 0.f;
    material.transmittance[i] = 0.f;
    material.emission[i] = 0.f;
  }
  material.illum = 0;
  material.dissolve = 1.f;
  material.shininess = 1.f;
  material.ior = 1.f;
  material.unknown_parameter.clear();
}

static bool exportFaceGroupToShape(
    shape_t &shape, std::map<vertex_index, unsigned int> vertexCache,
    const std::vector<float> &in_positions,
    const std::vector<float> &in_normals,
    const std::vector<float> &in_texcoords,
    const std::vector<std::vector<vertex_index> > &faceGroup,
    const int material_id, const std::string &name, bool clearCache) {
  if (faceGroup.empty()) {
    return false;
  }

  // Flatten vertices and indices
  for (size_t i = 0; i < faceGroup.size(); i++) {
    const std::vector<vertex_index> &face = faceGroup[i];

    vertex_index i0 = face[0];
    vertex_index i1(-1);
    vertex_index i2 = face[1];

    size_t npolys = face.size();

    // Polygon -> triangle fan conversion
    for (size_t k = 2; k < npolys; k++) {
      i1 = i2;
      i2 = face[k];

      unsigned int v0 = updateVertex(
          vertexCache, shape.mesh.positions, shape.mesh.normals,
          shape.mesh.texcoords, in_positions, in_normals, in_texcoords, i0);
      unsigned int v1 = updateVertex(
          vertexCache, shape.mesh.positions, shape.mesh.normals,
          shape.mesh.texcoords, in_positions, in_normals, in_texcoords, i1);
      unsigned int v2 = updateVertex(
          vertexCache, shape.mesh.positions, shape.mesh.normals,
          shape.mesh.texcoords, in_positions, in_normals, in_texcoords, i2);

      shape.mesh.indices.push_back(v0);
      shape.mesh.indices.push_back(v1);
      shape.mesh.indices.push_back(v2);

      shape.mesh.material_ids.push_back(material_id);
    }
  }

  shape.name = name;

  if (clearCache)
    vertexCache.clear();

  return true;
}

std::string LoadMtl(std::map<std::string, int> &material_map,
                    std::vector<material_t> &materials,
                    std::istream &inStream) {
  std::stringstream err;

  // Create a default material anyway.
  material_t material;
  InitMaterial(material);

  int maxchars = 8192;             // Alloc enough size.
  std::vector<char> buf(maxchars); // Alloc enough size.
  while (inStream.peek() != -1) {
    inStream.getline(&buf[0], maxchars);

    std::string linebuf(&buf[0]);

    // Trim newline '\r\n' or '\n'
    if (linebuf.size() > 0) {
      if (linebuf[linebuf.size() - 1] == '\n')
        linebuf.erase(linebuf.size() - 1);
    }
    if (linebuf.size() > 0) {
      if (linebuf[linebuf.size() - 1] == '\r')
        linebuf.erase(linebuf.size() - 1);
    }

    // Skip if empty line.
    if (linebuf.empty()) {
      continue;
    }

    // Skip leading space.
    const char *token = linebuf.c_str();
    token += strspn(token, " \t");

    assert(token);
    if (token[0] == '\0')
      continue; // empty line

    if (token[0] == '#')
      continue; // comment line

    // new mtl
    if ((0 == strncmp(token, "newmtl", 6)) && isSpace((token[6]))) {
      // flush previous material.
      if (!material.name.empty()) {
        material_map.insert(
            std::pair<std::string, int>(material.name, static_cast<int>(materials.size())));
        materials.push_back(material);
      }

      // initial temporary material
      InitMaterial(material);

      // set new mtl name
      char namebuf[TINYOBJ_SSCANF_BUFFER_SIZE];
      token += 7;
#ifdef _MSC_VER
      sscanf_s(token, "%s", namebuf, (unsigned)_countof(namebuf));
#else
      sscanf(token, "%s", namebuf);
#endif
      material.name = namebuf;
      continue;
    }

    // ambient
    if (token[0] == 'K' && token[1] == 'a' && isSpace((token[2]))) {
      token += 2;
      float r, g, b;
      parseFloat3(r, g, b, token);
      material.ambient[0] = r;
      material.ambient[1] = g;
      material.ambient[2] = b;
      continue;
    }

    // diffuse
    if (token[0] == 'K' && token[1] == 'd' && isSpace((token[2]))) {
      token += 2;
      float r, g, b;
      parseFloat3(r, g, b, token);
      material.diffuse[0] = r;
      material.diffuse[1] = g;
      material.diffuse[2] = b;
      continue;
    }

    // specular
    if (token[0] == 'K' && token[1] == 's' && isSpace((token[2]))) {
      token += 2;
      float r, g, b;
      parseFloat3(r, g, b, token);
      material.specular[0] = r;
      material.specular[1] = g;
      material.specular[2] = b;
      continue;
    }

    // transmittance
    if (token[0] == 'K' && token[1] == 't' && isSpace((token[2]))) {
      token += 2;
      float r, g, b;
      parseFloat3(r, g, b, token);
      material.transmittance[0] = r;
      material.transmittance[1] = g;
      material.transmittance[2] = b;
      continue;
    }

    // ior(index of refraction)
    if (token[0] == 'N' && token[1] == 'i' && isSpace((token[2]))) {
      token += 2;
      material.ior = parseFloat(token);
      continue;
    }

    // emission
    if (token[0] == 'K' && token[1] == 'e' && isSpace(token[2])) {
      token += 2;
      float r, g, b;
      parseFloat3(r, g, b, token);
      material.emission[0] = r;
      material.emission[1] = g;
      material.emission[2] = b;
      continue;
    }

    // shininess
    if (token[0] == 'N' && token[1] == 's' && isSpace(token[2])) {
      token += 2;
      material.shininess = parseFloat(token);
      continue;
    }

    // illum model
    if (0 == strncmp(token, "illum", 5) && isSpace(token[5])) {
      token += 6;
      material.illum = parseInt(token);
      continue;
    }

    // dissolve
    if ((token[0] == 'd' && isSpace(token[1]))) {
      token += 1;
      material.dissolve = parseFloat(token);
      continue;
    }
    if (token[0] == 'T' && token[1] == 'r' && isSpace(token[2])) {
      token += 2;
      // Invert value of Tr(assume Tr is in range [0, 1])
      material.dissolve = 1.0f - parseFloat(token);
      continue;
    }

    // ambient texture
    if ((0 == strncmp(token, "map_Ka", 6)) && isSpace(token[6])) {
      token += 7;
      material.ambient_texname = token;
      continue;
    }

    // diffuse texture
    if ((0 == strncmp(token, "map_Kd", 6)) && isSpace(token[6])) {
      token += 7;
      material.diffuse_texname = token;
      continue;
    }

    // specular texture
    if ((0 == strncmp(token, "map_Ks", 6)) && isSpace(token[6])) {
      token += 7;
      material.specular_texname = token;
      continue;
    }

    // specular highlight texture
    if ((0 == strncmp(token, "map_Ns", 6)) && isSpace(token[6])) {
      token += 7;
      material.specular_highlight_texname = token;
      continue;
    }

    // bump texture
    if ((0 == strncmp(token, "map_bump", 8)) && isSpace(token[8])) {
      token += 9;
      material.bump_texname = token;
      continue;
    }

    // alpha texture
    if ((0 == strncmp(token, "map_d", 5)) && isSpace(token[5])) {
      token += 6;
      material.alpha_texname = token;
      continue;
    }

    // bump texture
    if ((0 == strncmp(token, "bump", 4)) && isSpace(token[4])) {
      token += 5;
      material.bump_texname = token;
      continue;
    }

    // displacement texture
    if ((0 == strncmp(token, "disp", 4)) && isSpace(token[4])) {
      token += 5;
      material.displacement_texname = token;
      continue;
    }

    // unknown parameter
    const char *_space = strchr(token, ' ');
    if (!_space) {
      _space = strchr(token, '\t');
    }
    if (_space) {
      std::ptrdiff_t len = _space - token;
      std::string key(token, len);
      std::string value = _space + 1;
      material.unknown_parameter.insert(
          std::pair<std::string, std::string>(key, value));
    }
  }
  // flush last material.
  material_map.insert(
      std::pair<std::string, int>(material.name, static_cast<int>(materials.size())));
  materials.push_back(material);

  return err.str();
}

std::string MaterialFileReader::operator()(const std::string &matId,
                                           std::vector<material_t> &materials,
                                           std::map<std::string, int> &matMap) {
  std::string filepath;

  if (!m_mtlBasePath.empty()) {
    filepath = std::string(m_mtlBasePath) + matId;
  } else {
    filepath = matId;
  }

  std::ifstream matIStream(filepath.c_str());
  std::string err = LoadMtl(matMap, materials, matIStream);
  if (!matIStream) {
    std::stringstream ss;
    ss << "WARN: Material file [ " << filepath << " ] not found. Created a default material.";
    err += ss.str();
  }
  return err;
}

std::string LoadObj(std::vector<shape_t> &shapes,
                    std::vector<material_t> &materials, // [output]
                    const char *filename, const char *mtl_basepath) {

  shapes.clear();

  std::stringstream err;

  std::ifstream ifs(filename);
  if (!ifs) {
    err << "Cannot open file [" << filename << "]" << std::endl;
    return err.str();
  }

  std::string basePath;
  if (mtl_basepath) {
    basePath = mtl_basepath;
  }
  MaterialFileReader matFileReader(basePath);

  return LoadObj(shapes, materials, ifs, matFileReader);
}

std::string LoadObj(std::vector<shape_t> &shapes,
                    std::vector<material_t> &materials, // [output]
                    std::istream &inStream, MaterialReader &readMatFn) {
  std::stringstream err;

  std::vector<float> v;
  std::vector<float> vn;
  std::vector<float> vt;
  std::vector<std::vector<vertex_index> > faceGroup;
  std::string name;

  // material
  std::map<std::string, int> material_map;
  std::map<vertex_index, unsigned int> vertexCache;
  int material = -1;

  shape_t shape;

  int maxchars = 8192;             // Alloc enough size.
  std::vector<char> buf(maxchars); // Alloc enough size.
  while (inStream.peek() != -1) {
    inStream.getline(&buf[0], maxchars);

    std::string linebuf(&buf[0]);

    // Trim newline '\r\n' or '\n'
    if (linebuf.size() > 0) {
      if (linebuf[linebuf.size() - 1] == '\n')
        linebuf.erase(linebuf.size() - 1);
    }
    if (linebuf.size() > 0) {
      if (linebuf[linebuf.size() - 1] == '\r')
        linebuf.erase(linebuf.size() - 1);
    }

    // Skip if empty line.
    if (linebuf.empty()) {
      continue;
    }

    // Skip leading space.
    const char *token = linebuf.c_str();
    token += strspn(token, " \t");

    assert(token);
    if (token[0] == '\0')
      continue; // empty line

    if (token[0] == '#')
      continue; // comment line

    // vertex
    if (token[0] == 'v' && isSpace((token[1]))) {
      token += 2;
      float x, y, z;
      parseFloat3(x, y, z, token);
      v.push_back(x);
      v.push_back(y);
      v.push_back(z);
      continue;
    }

    // normal
    if (token[0] == 'v' && token[1] == 'n' && isSpace((token[2]))) {
      token += 3;
      float x, y, z;
      parseFloat3(x, y, z, token);
      vn.push_back(x);
      vn.push_back(y);
      vn.push_back(z);
      continue;
    }

    // texcoord
    if (token[0] == 'v' && token[1] == 't' && isSpace((token[2]))) {
      token += 3;
      float x, y;
      parseFloat2(x, y, token);
      vt.push_back(x);
      vt.push_back(y);
      continue;
    }

    // face
    if (token[0] == 'f' && isSpace((token[1]))) {
      token += 2;
      token += strspn(token, " \t");

      std::vector<vertex_index> face;
      while (!isNewLine(token[0])) {
        vertex_index vi =
            parseTriple(token, static_cast<int>(v.size() / 3), static_cast<int>(vn.size() / 3), static_cast<int>(vt.size() / 2));
        face.push_back(vi);
        size_t n = strspn(token, " \t\r");
        token += n;
      }

      faceGroup.push_back(face);

      continue;
    }

    // use mtl
    if ((0 == strncmp(token, "usemtl", 6)) && isSpace((token[6]))) {

      char namebuf[TINYOBJ_SSCANF_BUFFER_SIZE];
      token += 7;
#ifdef _MSC_VER
      sscanf_s(token, "%s", namebuf, (unsigned)_countof(namebuf));
#else
      sscanf(token, "%s", namebuf);
#endif

      // Create face group per material.
      bool ret = exportFaceGroupToShape(shape, vertexCache, v, vn, vt,
                                        faceGroup, material, name, true);
      if (ret) {
          shapes.push_back(shape);
      }
      shape = shape_t();
      faceGroup.clear();

      if (material_map.find(namebuf) != material_map.end()) {
        material = material_map[namebuf];
      } else {
        // { error!! material not found }
        material = -1;
      }

      continue;
    }

    // load mtl
    if ((0 == strncmp(token, "mtllib", 6)) && isSpace((token[6]))) {
      char namebuf[TINYOBJ_SSCANF_BUFFER_SIZE];
      token += 7;
#ifdef _MSC_VER
      sscanf_s(token, "%s", namebuf, (unsigned)_countof(namebuf));
#else
      sscanf(token, "%s", namebuf);
#endif

      std::string err_mtl = readMatFn(namebuf, materials, material_map);
      if (!err_mtl.empty()) {
        faceGroup.clear(); // for safety
        return err_mtl;
      }

      continue;
    }

    // group name
    if (token[0] == 'g' && isSpace((token[1]))) {

      // flush previous face group.
      bool ret = exportFaceGroupToShape(shape, vertexCache, v, vn, vt,
                                        faceGroup, material, name, true);
      if (ret) {
        shapes.push_back(shape);
      }

      shape = shape_t();

      // material = -1;
      faceGroup.clear();

      std::vector<std::string> names;
      while (!isNewLine(token[0])) {
        std::string str = parseString(token);
        names.push_back(str);
        token += strspn(token, " \t\r"); // skip tag
      }

      assert(names.size() > 0);

      // names[0] must be 'g', so skip the 0th element.
      if (names.size() > 1) {
        name = names[1];
      } else {
        name = "";
      }

      continue;
    }

    // object name
    if (token[0] == 'o' && isSpace((token[1]))) {

      // flush previous face group.
      bool ret = exportFaceGroupToShape(shape, vertexCache, v, vn, vt,
                                        faceGroup, material, name, true);
      if (ret) {
        shapes.push_back(shape);
      }

      // material = -1;
      faceGroup.clear();
      shape = shape_t();

      // @todo { multiple object name? }
      char namebuf[TINYOBJ_SSCANF_BUFFER_SIZE];
      token += 2;
#ifdef _MSC_VER
      sscanf_s(token, "%s", namebuf, (unsigned)_countof(namebuf));
#else
      sscanf(token, "%s", namebuf);
#endif
      name = std::string(namebuf);

      continue;
    }

    // Ignore unknown command.
  }

  bool ret = exportFaceGroupToShape(shape, vertexCache, v, vn, vt, faceGroup,
                                    material, name, true);
  if (ret) {
    shapes.push_back(shape);
  }
  faceGroup.clear(); // for safety

  return err.str();
}
}